Field of Science

Did Tetrapods Undergo a Postural Shift after the End-Permian Extinction?

Kubo, T. and M. J. Benton. 2009. Tetrapod postural shift estimated from Permian and Triassic trackways. Palaeontology 52:1029-1037. doi: 10.1111/j.1475-4983.2009.00897.x

Abstract- The end-Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.

3 comments:

  1. "...using a clear criterion for sprawling vs erect posture."

    wonder what that is - must be hard to define if the abstract is not more explicit.

    (Trackway width normalized by a measure of overall animal size? Or considering rotation of hand/ foot with respect to trackway midline? Or a linear combination of different trackway parameters also including pace angulation?)

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  2. "The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals..."

    No kidding? That is surprising to me if it is true about those intervals in general, and not just limited to certain localities.

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  3. Interesting article as for me. I'd like to read something more about this topic.
    By the way look at the design I've made myself Young escorts

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